Byff (バイフー Baifū ) is a massive white tiger from a faraway northern country. He is the familiar of a powerful witch, and was transformed into a beastman to serve her better. His master sent him to Bronquia in search of a book that "holds all of creation", which unbeknown to Byff himself is Nessiah's spellbook, the Revelation of the Gods. Gram Blaze encounters Byff searching through an empty mansion for books, and decides to bring him along to keep him out of trouble. Byff constantly makes puns, claiming that jokes are the basis of beastman communication, and does not always understand human values. He hates water. After the revolution, Byff departs in order to keep searching for the book, though he is implied to stay with the party in the alternate routes of Blaze Union. He is 202 cm tall and loves marshmallows. His voice actor is Tsuguo Mogami.
Byff's battle theme is NanTutTe (ＮａｎＴｕｔＴｅ).